1. Field of the Invention
The present invention relates generally to vehicle air conditioners, and particularly to a brushless motor having an outer rotor and used as a blower motor for a vehicle air conditioner.
2. Related Art
Conventionally, a brushless motor having an outer rotor and used as a blower motor for a vehicle air conditioner is mounted on a vehicle so that a rotation shaft of the motor extends vertically and the outer rotor is rotated horizontally. The brushless motor has a motor holder having a recessed portion and a stator fastened to a bottom of the recessed portion. The stator has a center piece, a core and plural windings wound on the core. The center piece is fastened to an upper surface of a mount plate fastened to the bottom of the recessed portion. A rotation shaft vertically extending through the center piece is rotatably held by bearings attached to the center piece. A cup-shaped rotor yoke is fastened to an upper part of the rotation shaft to cover the stator. A lower end of the rotation shaft passes through a through hole formed in the bottom of the recessed portion to be disposed below the motor holder.
The motor has a circuit substrate disposed below the motor holder. An exciting circuit for generating an exciting current to be supplied to the winding is mounted on the circuit substrate. Each of three terminals of the exciting circuit is upwardly extended through the through hole of the motor holder and a through hole formed in the mount plate. Then, each of the terminals is further extended outwardly in a radial direction of the center piece and is connected to each of the windings at a lower side of the core.
The motor holder has a cylindrical waterproof wall upwardly extending from a periphery of an opening of the recessed portion. A lower case is attached to the motor holder from below to cover the circuit substrate. A fan is attached to the upper end of the rotation shaft. When an exciting current generated by the exciting circuit is supplied to the windings, the rotor is rotated. As the rotor is rotated, the fan is rotated to blow air.
The brushless motor sucks therein air outside a passenger compartment of the vehicle through a duct. Therefore, when the vehicle is washed in a high-pressure car washing machine with the motor driven, the motor may also suck liquid such as water therein. The waterproof wall substantially restricts liquid from entering the recessed portion of the motor holder. However, when a relatively large amount of liquid is sucked by the motor or when air flow generated by the fan affects liquid flow, liquid may enter the recessed portion and make contact with each connection portion between the terminals and the windings. As a result, a short circuit between adjacent connection portions may occur. Further, liquid having entered the recessed portion may flow downwardly toward the circuit substrate through the through hole of the motor holder to cause various malfunctions of the motor.